1. Field of Invention
The present invention relates generally to the field of wireless communication and data networks. More particularly, in one exemplary aspect, the present invention is directed to methods and apparatus for correcting a loss of state machine synchronization between devices operating in a virtually connected communication mode.
2. Description of Related Technology
Paging mechanisms are used in many prior art wireless radio communication systems. Paging mechanisms allow a wireless device to minimize power consumption by operating in a reduced or “idle” state while unused. Once a wireless device receives a paging notification, it “wakes up” to respond. For example, Universal Mobile Telecommunications System (UNITS) is one exemplary implementation of a “third-generation” or “3G” cellular telephone technology. UMTS user equipments (UEs) support a variety of paging procedures to allow various network entities paging access to the UE.
The multiple paging procedures available to a UMTS UE are generally implemented within a state machine. As discussed in greater detail below with respect to FIGS. 1 and 2, the finite state machine (FSM) is implemented such that a cellular device operating in “idle” mode is inactive. An idle cellular device only periodically checks for “wake up” messages (e.g., paging notifications), or to transmit/receive a periodic device update. A cellular device operating in a connected state has a dedicated connection to the radio access network, and may actively send and receive data, while maintaining the radio connection.
When a cellular phone transitions its state, the UE and BS (base station) or RNC (Radio Network Controller) must initiate a connection which takes significant time and signaling overhead (the UE is unknown to the network, and must establish a connection via procedures for authentication, authorization, registration, etc.). Once connected, the UE may perform a myriad of data and/or control transactions with the network. The UE is assigned a temporary identifier, which allows the UE to be paged and resume the context of its previous operations; i.e., without re-establishing a connection.
Virtual connections may also be established, which enable a UE to remain, for the most part, relatively unencumbered by the processing and radio network management burdens of maintaining a radio connection. However, since the UE retains its temporary identifier, the UE can be quickly paged if necessary.
Unlike normal connectivity, virtual connectivity does not have a dedicated connection, and the UE can move into and out of cellular coverage, unnoticed by either the serving BS (or RNC) and the UE. Unfortunately, if a UE misses a page from the network in virtually connected operation (for example, if the UE has moved out of coverage), the network assumes the device has been dropped, or power cycled (i.e., that it has reset to an idle mode). The network switches to the legacy identity (e.g., IMSI, TMSI) for the UE. The UE, which is still operating in virtually connected mode, is oblivious to the RNCs state change. The loss of agreement on paging identification between the RNC and UE can be problematic at least.
Thus, improved methods and apparatus are needed which address the hazards related to virtual connection support. Such an improved solution should ideally operate substantially seamlessly and without adversely impacting user experience on legacy radio apparatus, and that of other wireless devices. The improved mechanisms should also robustly handle synchronization loss in virtually connected systems, while still preserving the benefits of the virtual connection.